The objectives of the proposed research are: (a) to investigate the role of cAMP, cGMP, PGE2 and PGF2 alpha in the mechanism of bone and PDL remodeling which occur during the processes of tooth eruption, root resorption and orthodontic tooth movement; (b) to study the effects of hormones (PTH and calcitonin), on cyclic nucleotides and prostaglandins in tissues surrounding erupting, resorbing and moving teeth; (c) to study the effects of imidazole (a stimulator of phosphodiesterase activity) and theophylline (a phosphodiesterase inhibitor) on cyclic nucleotides and prostaglandins in tissues surrounding erupting, resorbing and moving teeth. Cyclic AMP levels will be measured by a protein-binding technique; cGMP, PGE2 and PGF2 alpha will be measured by radioimmunoassays. The localization and distribution of cyclic nucleotides in jaw sections will be studied immuno-histochemically. Localizing cyclic nucleotides in mineralized tissues and measuring tissue concentrations of cyclic nucleotides and prostaglandins will further elucidate, on the cellular level, the mechanisms of tooth eruption, resorption and movement. The hormones and drugs will be employed as tools to modify the levels of tissue cyclic nucleotides during periods of tooth eruption, resorption and movement, in order to study the effects of these modifications on the remodeling process of the involved mineralized tissues.